I had a fouled spark plug on the number 2 cylinder and my mechanic said that I needed new valve seals in that cylinder, he replaced all of the valve seals on the passenger side as they were all going bad, 2 of the exhaust valve seals were almost totally disintegrated, I asked him about the driver's side and he said if it is not broke don't fix it, my thinking is there is no way that the passenger side cylinder heads could have bad valve seals and the driver's side cylinder head valve seals are fine. The engine has been Auto-Rxed and has 362,000 miles and it is definetly running better, should I check the plugs on the driver's side and do a compression test, will the compression test tell me if I have bad valve seals or good valve seals.